I begin by having students review what they know about magnetism from a previous lesson. Next I have them record today's focus question "How can you build the most powerful electromagnet?" in their science notebooks. After the question is recorded, I have them write what they want to know about electromagnets. I give them another opportunity to communicate by sharing these questions with each other.
After each student has had an opportunity to share, I draw a data table, and have students draw the table in their notebooks. I demonstrate a trial by picking up as paperclips, moving the magnet over a tub, and disconnecting the battery. I count the paperclips, and record the number in the data table. I then repeat the procedure for a 2nd trial. Not only is this valid scientific practice, it also allows more students within a group to be involved in a trial. I also record both values on a post it note, and add my data to the class scatter plot.
Next, it's time for them to make electromagnets. I remind them of expectations during group work, and have a representative from each group get one bolt, three wires, six post it notes, and a marker. I've cut the wires into different lengths between 20 and 50 cm in order to get a different number of wraps from each trial, and stripped the insulation from each end. I could have given each group their own battery, but because electromagnets have very little resistance, they use up batteries very quickly, and the entire circuits can get hot.
When groups are finished wrapping their wire, they conduct the trial with me to make sure it is done safely. I remind them to record their data both in their chart, and on a post it note for the class scatter diagram. After two trials, they remove the wire and repeat the process with each of the remaining wires.
As groups finish, I ask them to think about what they could change about their electromagnets that could be variables in an experimental question. When all groups have posted their results on the scatter diagram, I have them look at the results of the class, and record their conclusions in their science notebooks.